ATMS 360 Homework and Course Deliverables (return to main page)
[How to write lab report]


 

Assignment 5 Arduino and Atmospheric Measurements:

You will need to acquire data in class, write lab notes about your measurements, and write up each section of the lab
as homework as soon after the section is finished so you remember it in detail. It will be very difficult to write up the lab
after all the experiments are done.

Title: You can decide on the title based on your experience with this lab.

Goals:
a. Become familiar with the Arduino microcontroller as an example of a programmable device for acquiring measurements and controlling systems.
b. Demonstrate ability to modify Arduino sketches for solving problems.
c. Learn about and use sensors with atmospheric relevance.
d. Learn how to bring measurements from the Arduino into computers (interface the Arduino) to acquire data for later analysis and display.

If possible, install the Arduino software on your own laptop (if you have one), and use it in class.
Also download CoolTerm and place it somewhere that you can get to it for ease of use. This program allows us to transfer data from the Arduino to the computer.
The code for the projects in the book and kit is here: expand the file and put the folder in your Arduino examples folder.
Here is a link to the an online version of a manual that is similar to the one we use in class. (local backup).

In your report, describe and/or answer these questions
1. Introduction to describe the Arduino (why is everyone so crazy about this thing?).

Measurements and Analysis
2. Do Circuit 6, pg 40 in the book to learn about the photoresistor and how to measure its output.
Then create a circuit to drive the LED at different frequencies to see if the photoresistor resistance can accurately follow the LED output for low and high frequencies.
Point the LED output directly into the photoresistor input. You can use variable delay and the 'Blink' sketch to drive the LED.


Description of the circuit for the photoresistor test. Click on the image for a larger version.

If the LED is driven by a square wave, the photoresistance should show a crisp square wave too. Use the plot monitor on Arduino to view the photoresistor output,
and save some data with CoolTerm (including time) so that you can graph the photoresistor output from the LED drive as a function of time.
Can you estimate the time constant of the photoresistor as a sensor of light?
Here's an example sketch that may be helpful in measuring response time. You may find ways of speeding it up to get more time resolution on the LED response.


3. Do Circuit 7, pg 44 in the book to be become familiar with the TMP36 temperature sensor.
What is the principle of operation of the TMP36 temperature sensor? How was its signal obtained?

Description of the analog to digital conversion for the TMP36 sensor. Click on image for a larger version.

Example sketch for response time measurement. Read it and follow instructions. Pinch the temperature sensor to warm it up when the LED comes on.
Record a time series with CoolTerm as you pinch the the sensor to warm it up to a steady temperature, and let it decay to a lower temperature.
Estimate the time constant for the sensor as you are warming it up with your fingers, and the time constant as you are cooling it off by letting it sit in air.

4. Create a voltage divider circuit to measure the resistance of the thermistor sensor using a fixed resistance of 1 MegOhm (1,000,000 ohms).
Calculate the temperature that corresponds to your measured resistance using the equation given here (thanks Alex).
Record a time series using CoolTerm as you pinch the the sensor to warm it up to a steady temperature, and let it decay to a lower temperature.
Estimate the time constant for the sensor as you are warming it up with your fingers, and the time constant as you are cooling it off by letting it sit in air.
Here's an example sketch to use for the thermistor sensor evaluation. Read the sketch for instructions on what to do.
Pinch the thermistor carefully (without affecting the wires) when the LED is on.

Click on image for larger version.

5. Set up a circuit and sketch to acquire data from the pressure sensor. Do appropriate data averaging so that you can easily tell the pressure difference
between having the sensor on the desk, and having the sensor about 1 meter higher or lower. Record data with CoolTerm to demonstrate your results.
Here's an example sketch for the pressure sensor. You'll have to comment out some lines near the end to get only the pressure measurements to CoolTerm.
Do measurements with 1 second time average, holding the sensor down for 10 seconds, then up for 10 seconds.
Then modify the code to obtain 10 second time averages. Test by holding the sensor low for 100 seconds, and high for 100 seconds.
Comment on the effects of additionally time averaging the data.

Click on image for larger version.

Note: It seems the 10 bit analog to digital (a/d) converter of the Arduino would not be able to resolve a pressure difference of about 0.1 mb associated with
1 meter height difference. 1 bit change in the a/d counts corresponds to a voltage change of about 0.005 volts, and a pressure change of and about 1 mb pressure.
Dither helps: the voltage source for the Arduino is noisy enough to cause around 50 mv or so of noise so that the a/d counts fluctuate to a useful average.
The example sketch for pressure averages the measurements of the pressure sensor voltage and the voltage divider voltage about 1800 times for each measurement.
Use of the voltage divider for the power supply voltage measurement is necessary since the a/d range is 5 volts, and direct measurement might be over the measurement range.

If you are ahead, you may add the digital pressure sensor to the sketch and breadboard layout and compare the analog and digital sensors.

6. Implement the infrared sensor. Interface it with Labview using the indicated code.
Demonstrate a time series of temperature from Labview or cool term by doing a screen capture. Include a discussion of how the sensor works.
Those with laptops can take the IR sensor outside to get a time series of infrared brightness temperature of various targets.


Notes on the IR sensor: Click on image for larger version.


Resources:
Description of the Arduino and some sensors we'll use.

TMP36 temperature sensor data sheet.

Very useful voltage divider circuit to use for measuring sensors that depend on resistance.

Click on image for larger view.

 

 

 

 

 

 

Assignment 4

Title: Vertical distribution of pressure, temperature, and dew point temperature inside and outside the Physics building: Analogy for weather balloon sampling in the atmosphere.

Here's a virtual tour of the Reno National Weather Service balloon launch facility.

Goals:
a. To investigate the vertical distribution of atmospheric thermodynamic properties, in analogy to balloon sampling in the atmosphere.
b. To appreciate the time constant of sensors, and how measurement strategy needs to account for it.
c. To use custom instruments to better understand the components.
d. To use a simple method for sampling near surface atmosphere properties.

Measurements:
We have 4 'Teensy' data cards for use in this lab, and 8 microSD cards. You can work in groups of 2 to acquire data, but each person will process the data.
We get data off the cards using microSD cards. Measurements include pressure, temperature, relative humidity, and GPS latitude, longitude, and height.
GPS measurements won't be useful for this exercise.

a. We will first evaluate the pressure sensor to gain a sense of its ability to measure vertical variations of pressure.
After clearing the data acquisition cards, turn the sensor on. Let it warm up for about a minute. Note the pressure measurement.
Then raise the sensor overhead for 5 to 10 seconds. Note the pressure change. Then lower it to the ground for 5 to 10 seconds and note the pressure change.
Repeat this procedure 3 times. After step b., you will be taking the data off of the microSD card and can make a time series graph of pressure.
Note the altitude changes and the stability of the sensor.

b. Next we measure the time constant of the temperature, relative humidity, and pressure sensors so we know this important sensor property.
Instrument/sensor time constant is the time it takes to respond to a changed value.
The instrument should start at room temperature, after performing part a.
Then step outside into the cold shade, making sure the sensor doesn't get heated by the sun.
Wait until the temperature and dew point temperature come to equilibrium outside (about 10 or 15 minutes).
Come back inside after 5 minutes. Again wait 5 minutes inside for the sensor to warm up.
Then go to the lab and get the data off of the Teensy microSD card.
Make a time series plot of temperature and relative humidity.
Examine your time series.
We will fit an exponential curve to the time series and use the fit parameters to get the time constant.
This exercise will introduce you to the 'solver' in Excel and how to use it to obtain parameters from measurements.
The basic philosophy of the solver is this: minimize the error by letting the solver change the model parameters p1, p2, and p3.
It's best to have a lot of redundancy, many more measurements with information content than model parameters.

Temperature time constant notes. Click on image for larger version.

c. Also make a time series of the pressure measurements that were obtained during the temperature and RH measurements. This data will be good to gain a sense of the fluctuation of pressure, and the ability of the instrument to accurately measure pressure.

d. Next we will do measurements of the vertical distribution of temperature, RH, and pressure in the Physics building.
Start at the basement level of the Physics building.
Measure the vertical distribution of T, Tdew, and pressure in the Physics building, from the basement to 4th floor.
Be sure you wait long enough on each level of the Physics building for the sensors to come to equilibrium (the time constant from part a.).
You may use the DRI station pressure to see if the pressure was actually 'constant' during the time of our measurements.
Then return to the basement rapidly so that the pressure sensor value doesn't change if the ambient pressure is changing a lot during the day.
Calculate the height of the building by using an appropriate equation and your measurements, starting with zero meters at the basement level.

e. Measure the actual height of the this distance using a ruler to measure step size, and to count the number of steps. (Is step size similar from step to step?)

NOTES ON THEORY FOR DETERMINING THE TIME CONSTANT, AND FOR CONVERTING PRESSURE TO HEIGHT.

(click on images for larger version).

H=scale height of atmosphere, calculated as shown.
RD = 287.1 Joules/(kg K) is the gas constant for air.
We'll use the simple approach to get the height from pressure,
(see the circled equation on the figure to the right).

Use the circled equation for converting pressure to height.
Note that z=0 meters when P(z)=Po.
The noise on the pressure sensor of about 0.02 mb gives a height
uncertainty of about 21 cm.

This general approach could be used to obtain pressure.
It is more accurate when the temperature changes a lot between
pressure levels.

Here is the equation we used and fitted to obtain the time constant for the temperature sensor.

In your report:
1. Measurements section should describe sensors used, see resources below.
2. Define and discuss the time constant for the temperature and relative humidity measurements, showing your data and the fit to it to obtain the value. Discuss how the measurement was obtained.
3. Use the pressure measurements from the day of the temperature time constant measurements to discuss the pressure sensor noise, and the ability to see pressure fluctuations from ground level to above your head.
4. Discuss methodology and calculation of obtaining building height from the basement to the roof from pressure measurements, and uncertainty in this measurement.
5. Measure the height of a step and count the total number of steps in the building from the basement to the roof. Compare with the height obtained in question 4.

Here's a summary of the graphs needed for your report. Click on each image to obtain a larger size.

Resources:
Pressure Sensor (Transducer) MPX 4115 APand application note on how to filter the output
Temperature and humidity sensors made by Sensirion
Schematic and board layout, and the program for the Teensy microcontroller based package, in case you are interested (It is not a requirement for this assignment to describe/understand the entire system, just become familiar with the sensors.)

Literature to help with the introduction, though you can use others as well:
Radiosonde paper.
National weather service upper air measurements made with balloons (complementary site).
Tethered kites used to sample in the vertical.
Smart balloons for measuring along with a moving air masses.

 

 

 

 

 

 

Assignment 3

The goal of this quick-study style lab is to become familiar with meteorological radar used to measure precipitation.
Examples are on this page.

Submission through webcampus is preferred. Copy these questions to MS word and work on them.
Be sure to give your sources for answers. We'll go through this in class.

Basics:
1. What diameter range are raindrops?
2. What is the shape of raindrops?
3. Why don't raindrops get arbitrarily large?

Local Rain Measurements:
4. What is the rainfall rate equation?
5. How does a simple rain gauge work?
6. How does a tipping bucket rain gauge measure rain?
7. How does a disdrometer work?

Weather Radar basic presentation; brief presentation for dbZ; animation
8. What is the name of weather radars used by the National Weather Service?
9. What wavelength range used by this radar?
10. Briefly, how does radar work to measure rain?
11. Calculate the size parameter x=2 pi * Raindrop Radius / radar wavelength.
12. What 'radiation regime' is the size parameter of equation 11? Note that it is the same radiation regime that gives rise to the blue sky on a clear day. Note.
13. What is the basic relationship for radar backscattering in terms of number of raindrops per volume, back scattering strength, droplet diameter D, and radar wavelength lambda? Note.
14. Why must the radar be empirically calibrated given question 13, and question 4?
15. How does Doppler radar work? What can be detected with it?
16. How does dual polarization radar work, and what can be detected with it?

 

 

 

 

Assignment 2

Purpose: Broad overview of atmospheric instrumentation measurements.

This is an online homework assignment and is described on webCampus.

 

 

Assignment 1

Purpose:
To explore radiosonde measurements of atmospheric properties around the world.
To establish the format and style needed for report writing for rest of the semester, and thereafter.
To visit the Reno National Weather Service (NWS) office to watch a balloon launch, and to learn about what they do.
We have a visit to the Reno NWS office on the 30th of January in the afternoon. Here's the location.

Turn in this homework assignment through webCampus.

Prepare a report using Google Earth, MSword, and Excel to explore the following.

Meteorology of the world: Use Google Earth to view these two locations, Rochambeau French Guiana and Barrow Alaska USA.
Look at data for 12Z, 8 January 2018
Near equator: Rochambeau French Guiana (get sounding for SOCA from the Wyoming site, plot pressure and temperature vs height, calculate density and plot versus height)
Near north pole: Barrow Alaska (get sounding for PABR from the Wyoming site, plot pressure and temperature vs height, calculate density and plot versus height)
Then fit a trendline for ln(Pressure) vs height to obtain the scale height of the atmosphere at these two locations, considering data to a height of 2 km, using the solver in Excel for doing the fitting.
Compare and contrast the difference in the meteorology between these two sites for 8 January 2018.

TOOLS:
A. Meteorological data can be obtained from the University of Wyoming web site.
B. Most (or all) computers readily accessible to all students, using their netID, have Google Earth, MSword, and Excel.
C. You can use your netID to also access these software packages through the UNR remote services application.
D. Students should be able to install MS Office software packages on their own computers as well.

E. National weather service site describing radiosonde measurements.
F. Reno National weather service site providing a virtual tour of radiosonde launches.
G. Grand Junction Colorado NWS site discussing radiosonde data.

H. Raw data from the balloon launch we attended on Tuesday, 30 January 2018, in case we work more with it.

 


EXPECTATIONS IN LAB REPORTS

Lab reports will be written the same format we use for scientific papers and for student senior, MS, and PhD theses.
One goal of this class is to work on your ability as a science writer.
Let me emphasize one word here. SCIENCE SCIENCE SCIENCE SCIENCE SCIENCE SCIENCE!!!!
So often we are obsessed with the technical details of the measurements that we don't cover the science adequately.
The following elements are needed for your lab report to be complete.
Here is an example of some hints I found using a google search with the keyword "how to write a scientific paper".
Page length doesn't matter; it's all about the contents.
Make it as short as possible to get the message across in a clear manner.

Title: The title should cover the science objective and maybe mention the instrument(s) used for the measurement.

Abstract: The abstract is a brief discussion of the findings of your work. It should be well written because it is often what is read as someone makes a decision to read your work (or fund your research).
Hint on writing abstracts.

Introduction: Explain the scientific goal in more detail and maybe hint at the measurement methods used.

Measurements: Discuss the measurement methods, including uncertainties.
Discuss the instrument(s) and the pertinent information needed to convey what you measured.

Observations: Display your observations and interpret them for your reader.
Make clear, legible graphs with large fonts, clear symbols, and clearly documented results.

Figures: Provide figures, each figure with a number and caption.
Figures must be in publication format -- high quality figures with 16 point (or greater) bold black font; tick marks inside.
All axes 1 point thick and black.
Each figure must be discussed in the text by number, describing the significance of the figure and its relationship to other figures as needed.

Equations: Equations should be offset, as in a textbook, and each equation should have a number.
Refer to equations by number in the text.

Conclusions: The conclusion should summarize your observations and perhaps make suggestions for future work.

References: References refer to specific articles and/or books, etc, that you reference in your paper.

HERE IS AN EXAMPLE LAB REPORT

HERE IS ANOTHER EXAMPLE LAB REPORT


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